This invention relates to the manufacture of colored, tinted and coated plate glass and the plate glass or spandrel product provided by such manufacture.
The invention further relates to a method of opacifing glass and the opacified glass product produced by that method.
With the evolution in modern, glass-expansive architecture, the use of glass as a structural component has increased. With this use of glass, the control of heat and light transmission through the glass has become the focus of much engineering effort. A simple, economic and efficient method of manufacturing opacified glass has always been desirable.
Ceramic frit is the oldest method of opacifing glass. It utilizes glass enamels comprised of ceramic frit that are permanently fused to the glass. The frit materials can be applied to the glass by spray, by roller, by curtain coating or by screen printing. Either the frit is colored or pigments, usually metal oxides, are added. This particulate material is suspended in a media which can vary from water to oil to any of a number of organic chemicals depending upon the selection of the method for applying the material to coat the glass surface.
Usually only one surface, the top surface, is coated at a time and then the glass is heated to fuse the material to the glass surface.
A second method for opacifing glass is to apply plastic film opacifiers. In this method an adhesive is used to adhere the plastic film to the glass. Polyproplyene and polyethylene have been used as they can be glued to glass. The polypropylene and the polyethylene polyester sheets are tinted before gluing. Heat build up, however, can cause a separation of the glued surfaces and/or a discoloration of the glue material used after the opacified glass product has been installed and subjected to ultraviolet light and heat build up from the sun. Polypropylene and polyethylene have limited uses as they are translucent and not transparent.
Another method of opacifing glass is to coat it with a colored silicone elastomer. As an example an 8-mil thickness of the silicone material is sprayed on the glass. This material contains a neutral-cure silicone sealant. The material dries at room temperatures in hours or can be oven dried in minutes. Adhesion is achieved but the silicone coating has yet to be proven in long term applications. Likewise, it is subject to abrasion damage during manufacture or construction.
A further type of opacified glass is made by vacuum deposition of metal to glass. This creates a very thin layer of material, microns thick which is very susceptible to abrasion and scratching.
Tinted polycarbonate sheet and polyvinyl butyral sheet, the PVB has a natural brown tint, have been laminated to glass using an acrylic coupling medium and a mechanical bond, respectively. These materials, however, tend to discolor over time. Further, all polycarboniates require a cross-linking agent, usually alkaline based, to etch the glass to enhance adhesion. This cross-linking bonding agent adds to the manufacturing expense.
Architectural spandrel glass has also been made by painting one side with a ceramic paint and then thermo-bonding the paint by heating. This type of glass also tends to discolor over time. Further, its color "hue" is difficult to control from one manufacturing run to another.
Of all the presently known laminate materials, polyurethane offers the best performance. It is more moisture proof than polycarbonate and won't discolor over time as polycarbonate does when it picks up moisture. It is crystalline and has good bondability to glass especially when a coupling agent is used. However, heretofore, polyurethane has only been successfully applied to glass as a liquid in a casting process.
The "floating" of a cast polyurethane layer on a sheet of glass has been a cumbersome and slow manufacturing process.
What is desired is an improved process for manufacturing colored or tinted spandrel glass and architectural glass whereby this glass is more easily manufactured from less costly materials.
What is also desired is an opacified glass which is more easily and more economically manufactured and which is color stable and transparency stable with time.
What is further desired is an opacified architectural glass laminate and a manufacturing process where color hue is easily stabilized between manufacturing runs.